The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Some embodiments relate to methods applied to a well bore penetrating a subterranean formation.
Hydrocarbons (oil, condensate, and gas) are typically produced from wells that are drilled into the formations containing them. For a variety of reasons, such as inherently low permeability of the reservoirs or damage to the formation caused by drilling and completion of the well, the flow of hydrocarbons into the well or the well injectivity is undesirably low. In this case, the well is treated with a treatment fluid, which can include fluids for fracturing, diversion, or stimulation to increase the production of oil or gas or to improve well injectivity. For stimulation, the use of acids is frequently employed. Acid fracturing and matrix acidizing are widely used techniques for increasing the production of oil or gas from a well that penetrates an underground carbonate formation, e.g., a limestone or dolomite hydrocarbon bearing formation.
Fines (such as sand) migration can also be an issue, resulting in rapid productivity decline and/or erosion damage to downhole and surface hardware. In such cases, the well can be treated with a treatment fluid, which can include fluids for sand control.
Unwanted water production can result in decreased oil production in a well. In such cases, the well can be treated with a treatment fluid, which can include fluids for water control.
In matrix acidizing treatments, acid is injected at a pressure below the fracture pressure of the formation to remove near wellbore damage and increase productivity in some cases through the creation of vugs and wormholes that extend from the wellbore into the formation. To more fully stimulate a formation with zones of varying permeability, diversion stages are employed to temporarily block areas of higher permeability and send acid to lower permeability zones. The diverter must eventually degrade or be removed to allow the stimulated zones to communicate with the wellbore. This process can be performed multiple times with corresponding acid stages to provide diversion and stimulation of multiple zones in a well. During matrix acidizing treatments, the effectiveness of the diverter relies on how well the diverting material restricts access to the high permeability zones.
In sand control treatments, unconsolidated formation materials are held together by mechanical means such as screens and/or gravel packs, or by chemical means such as resins. This treatment keeps the formation intact during well production to avoid producing materials that might otherwise come free of the formation that might damage or plug equipment. Sand control treatments can be performed on more than one area of a well, e.g., within layers of varying height and permeability. To divert a sand control treatment fluid to less permeable zones of the well, either mechanical devices such as packers, sleeves, or valves or chemical methods may be used.
As an added complexity, treatments performed with coiled tubing require that diverting materials must be able to pass through the coiled tubing string, which may contain a complex flow path, very small exit points, or other constrictions, and/or instruments sensitive to fluid friction or drag. For example, a small deposition of even a partial plug in a coiled tubing might impose sufficient drag on a distributed sensor cable to stretch or break it and ruin the cable. These limitations create an environment that limits the applicability of many diverting materials for delivery through coiled tubing.
As a further complexity, there are difficulties in employing chemical diverting materials in conjunction with mechanical sand control devices because the diverting agents tend to accumulate on the mechanical control devices and cannot adequately divert from the desired zone to be plugged.
The industry would welcome methods to address one or more of the foregoing limitations.